It is customary in the airline industry to provide food and beverages on flights to the passengers as well as the crew. Depending upon the duration of the flight, the service can be as little as beverages and a light snack to multiple meals for longer flights. To store, prepare, and serve food and beverages on an aircraft requires that provisions be made to the aircraft to safely maintain the food and drinks in a proper manner. For perishables, that means preserving the food and drinks in an environment that will keep the products fresh and viable. In most cases, this means a refrigeration system that can store and chill food and beverages until they are ready to be served to the passengers.
Large commercial passenger carrying airplanes predominantly utilize one of two cooling systems for maintaining perishable food stuffs and non-perishable beverages at their optimum temperatures. Chilling is necessary to preserve perishables and make certain beverages and foods more palatable, especially during long haul and ultra-long haul aircraft journeys. The first cooling system utilizes a standard vapor cycle based air chiller that utilizes conventional refrigerant vapor compression and expansion technology to generate a secondary re-circulated chilled air loop. The chilled air is generally supplied and returned via thermally insulated air ducting to and from a suitable storage structure, such as a galley. The air chiller may be located in the galley, or mounted proximally in another part of the aircraft airframe.
The second type of cooling system utilizes the same conventional refrigerant vapor compression and expansion technology, but the cooling medium is a chilled liquid rather than a air. Chilled liquid has a higher thermal capacity but requires more sophisticated pumping and conduit architecture to operate the system. The chilled liquid is pumped in a closed loop to and from a suitable storage structure such as a galley. The chilled liquid in some cases is configured to serve a large centralized system for the whole aircraft. In other cases, the chilled liquid can be circulated at each separate galley compartment to form a local area chilling loop, or be based on each individual galley as a standalone system. At the galley, the liquid is passed via a control valve and electronic control system to a heat exchanger, where an electric axial (or other) fan blows or sucks air through its matrix and to the storage compartment that requires chilling, such as, for example, a galley cart bay or refrigeration compartment. The heat exchanger fan and its control system (though not necessarily all) are grouped together to form a chilled air recirculation unit that may be fitted in or on the galley or remotely from it, or the galley complex.
One drawback of these various chiller systems is that they take up a large percentage of available space in the galley, which is at a premium in an aircraft for obvious reasons. Further, the chillers tend to be very heavy, which is also a drawback to their use on aircraft. There are also issues with condensation collection and removal, and the need for improvements in heat transfer efficiency. Accordingly, it would be beneficial to have a chiller system that takes up less space and reflects a reduction in weight over conventional chiller systems currently in use, while providing for condensation collection and improved heat transfer efficiency.